Insofar as we are aware, the so-called ASOPS approach represents the best present state of the art of such apparatus and method.
Elzinga et al, for example, in an article entitled "Pump/Probe Method for Fast Analysis of Visible Signatures Utilizing Asynchronous Optical Sampling" (ASOPS), in Applied Optics, Vol 26, No. 19, pp 4303-4309, Oct. 1, 1987, describe monitoring subnanosecond excited-state processes by stimulating a process with pump pulses from a mode-locked laser and probing it with probe pulses from an asynchronously pumped laser. The two lasers operate at slightly different repetition rates, so a repetitive relative phase walk-out of pump and probe pulses occur.
In other prior pump/probe methods, the pump and probe pulses run at identical repetition rates, with an optical delay line used to control relative timing between the pulses.